A filter assembly is commonly installed upstream of the air intake of a combustion engine. Such a filter assembly can generally comprise a housing, a primary filter cartridge, and a secondary filter cartridge. During normal operation, air entering the filter assembly must pass through the primary filter cartridge (or more particularly its filtering media), then through the secondary filter cartridge (or more particularly its filtering media), to exit the filter assembly. Thus, only filtered air can exit the filter assembly and pass to the engine.